1. Field of the Invention
This invention resides in an improved cylindrical air gap machine having increased efficiency. The machine has increased surface area in the air gap by changing the smooth cylindrical surfaces of the rotor and stator to surfaces with grooves forming a serrated profile.
In an induction type machine and a direct current type machine, the power output of said machines depends upon the produced magnetic flux that crosses an air gap between the rotor and the stator in the machine. If the air gap or the air gap flux density between the surface areas of the rotor and stator are too large, a large loss in ampere turns is noted because of the increased energy required.
In the past, others have tried to solve the energy loss across the air gap in cylindrical machines by increasing the length of the rotor and stator or by decreasing the air gap between the rotor and stator. Both of these methods suffer from the disadvantage of requiring an increased diameter motor shaft because of magnetic side pull. Another disadvantage is that a larger machine is required to obtain the desired performance.
2. Description of the Prior Art
Numerous attempts have been made in the past to increase the efficiency and reduce the energy consumption of electric machines.
U.S. Pat. No. 3,296,475 to Parker relates to dynamo-electric machines, rotors therefor. The patent describes an axial air gap machine having a lower rotor resistance thereby reducing power losses in said machine.
U.S. Pat. No. 3,304,450 to Bask, Jr., et al., describes an axial air gap dynamo-electric machine, wherein said machine is brushless and contains a rotor spaced apart from a stator armature by an axial air gap. A rotor disc, as described above, has at least one of its sides juxtaposed to a stator core provided with an armature winding with a narrow axial air gap between the faces of the stator and of the rotor.
U.S. Pat. No. 3,581,389 to Mori, et al., discloses a method for producing a magnetic core for an electric rotating machine which has an axially spaced air gap as in the case of a disc-type rotating machine.
U.S. Pat. No. 4,207,487 to Beyersdorf describes a disc-type, dynamo-electric machine having two stators and one rotor, active air gaps between each stator and the rotor, two annular energizing windings in the stators, and two non-active or auxiliary air gaps formed in a smooth region between the stators and the rotor.
U.S. Pat. No. 5,093,596 to Hammer relates to a combines linear-rotary direct drive step motor which provides both linear and rotary motion over a predefined range, e.g. along a portion of the longitudinal axis of the rotor shaft. The rotor and stator of the rotary step motor are described as having teeth.
U.S. Pat. No. 5,177,392 to Scott discloses a disc-type machine having a plurality of alternating stator and/or rotor sections. The stator has micro-laminated stator teeth molded from cut steel particles, mounted on a large disc of composite fiber material which is the main structure component of each stator section.
U.S. Pat. No. 5,777,421 to Woodward Jr. teaches a disc-type electrical machine having enhanced efficiency and effectiveness. The machine comprises a housing unit, a stator connected to said housing unit, a shaft rotateably connected to the stator housing unit with rotation means. A rotator connected to the shaft wherein the stator surface area and the rotor surface area are serrated.
It can readily be seen that serrated air gap surfaces improve efficiency of machines. However, a change in the rotor and a major change in the stator would be required for cylindrical machines to obtain the desired efficiency.
A magazine entitled "MACHINE DESIGN", a Penton Publication which was published Dec. 16, 1965 and entitled "ELECTRICAL MOTOR" describes different types of electrical motors and what they are used for. The article gives a laundry list of electrical motors and companies as well as new materials used to construct said motors.